[PATCH v6 14/18] staging: rtl8192u: ieee80211: Convert from ahash to shash

[Kees Cook]

This is an identical change to the wireless/lib80211 of the same name.
In preparing to remove all stack VLA usage from the kernel[1], this
removes the discouraged use of AHASH_REQUEST_ON_STACK in favor of
the smaller SHASH_DESC_ON_STACK by converting from ahash-wrapped-shash
to direct shash. By removing a layer of indirection this both improves
performance and reduces stack usage. The stack allocation will be made
a fixed size in a later patch to the crypto subsystem.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 .../rtl8192u/ieee80211/ieee80211_crypt_tkip.c | 57 +++++++++----------
 1 file changed, 28 insertions(+), 29 deletions(-)

diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
index a7efaae4e25a..1088fa0aee0e 100644
--- a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
+++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
@@ -54,9 +54,9 @@ struct ieee80211_tkip_data {
 	int key_idx;
 
 	struct crypto_skcipher *rx_tfm_arc4;
-	struct crypto_ahash *rx_tfm_michael;
+	struct crypto_shash *rx_tfm_michael;
 	struct crypto_skcipher *tx_tfm_arc4;
-	struct crypto_ahash *tx_tfm_michael;
+	struct crypto_shash *tx_tfm_michael;
 
 	/* scratch buffers for virt_to_page() (crypto API) */
 	u8 rx_hdr[16], tx_hdr[16];
@@ -80,8 +80,7 @@ static void *ieee80211_tkip_init(int key_idx)
 		goto fail;
 	}
 
-	priv->tx_tfm_michael = crypto_alloc_ahash("michael_mic", 0,
-			CRYPTO_ALG_ASYNC);
+	priv->tx_tfm_michael = crypto_alloc_shash("michael_mic", 0, 0);
 	if (IS_ERR(priv->tx_tfm_michael)) {
 		printk(KERN_DEBUG "ieee80211_crypt_tkip: could not allocate "
 				"crypto API michael_mic\n");
@@ -98,8 +97,7 @@ static void *ieee80211_tkip_init(int key_idx)
 		goto fail;
 	}
 
-	priv->rx_tfm_michael = crypto_alloc_ahash("michael_mic", 0,
-			CRYPTO_ALG_ASYNC);
+	priv->rx_tfm_michael = crypto_alloc_shash("michael_mic", 0, 0);
 	if (IS_ERR(priv->rx_tfm_michael)) {
 		printk(KERN_DEBUG "ieee80211_crypt_tkip: could not allocate "
 				"crypto API michael_mic\n");
@@ -111,9 +109,9 @@ static void *ieee80211_tkip_init(int key_idx)
 
 fail:
 	if (priv) {
-		crypto_free_ahash(priv->tx_tfm_michael);
+		crypto_free_shash(priv->tx_tfm_michael);
 		crypto_free_skcipher(priv->tx_tfm_arc4);
-		crypto_free_ahash(priv->rx_tfm_michael);
+		crypto_free_shash(priv->rx_tfm_michael);
 		crypto_free_skcipher(priv->rx_tfm_arc4);
 		kfree(priv);
 	}
@@ -127,9 +125,9 @@ static void ieee80211_tkip_deinit(void *priv)
 	struct ieee80211_tkip_data *_priv = priv;
 
 	if (_priv) {
-		crypto_free_ahash(_priv->tx_tfm_michael);
+		crypto_free_shash(_priv->tx_tfm_michael);
 		crypto_free_skcipher(_priv->tx_tfm_arc4);
-		crypto_free_ahash(_priv->rx_tfm_michael);
+		crypto_free_shash(_priv->rx_tfm_michael);
 		crypto_free_skcipher(_priv->rx_tfm_arc4);
 	}
 	kfree(priv);
@@ -500,30 +498,31 @@ static int ieee80211_tkip_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 	return keyidx;
 }
 
-static int michael_mic(struct crypto_ahash *tfm_michael, u8 *key, u8 *hdr,
+static int michael_mic(struct crypto_shash *tfm_michael, u8 *key, u8 *hdr,
 		       u8 *data, size_t data_len, u8 *mic)
 {
-	AHASH_REQUEST_ON_STACK(req, tfm_michael);
-	struct scatterlist sg[2];
+	SHASH_DESC_ON_STACK(desc, tfm_michael);
 	int err;
 
-	if (tfm_michael == NULL) {
-		printk(KERN_WARNING "michael_mic: tfm_michael == NULL\n");
-		return -1;
-	}
-
-	sg_init_table(sg, 2);
-	sg_set_buf(&sg[0], hdr, 16);
-	sg_set_buf(&sg[1], data, data_len);
+	desc->tfm = tfm_michael;
+	desc->flags = 0;
 
-	if (crypto_ahash_setkey(tfm_michael, key, 8))
+	if (crypto_shash_setkey(tfm_michael, key, 8))
 		return -1;
 
-	ahash_request_set_tfm(req, tfm_michael);
-	ahash_request_set_callback(req, 0, NULL, NULL);
-	ahash_request_set_crypt(req, sg, mic, data_len + 16);
-	err = crypto_ahash_digest(req);
-	ahash_request_zero(req);
+	err = crypto_shash_init(desc);
+	if (err)
+		goto out;
+	err = crypto_shash_update(desc, hdr, 16);
+	if (err)
+		goto out;
+	err = crypto_shash_update(desc, data, data_len);
+	if (err)
+		goto out;
+	err = crypto_shash_final(desc, mic);
+
+out:
+	shash_desc_zero(desc);
 	return err;
 }
 
@@ -663,9 +662,9 @@ static int ieee80211_tkip_set_key(void *key, int len, u8 *seq, void *priv)
 {
 	struct ieee80211_tkip_data *tkey = priv;
 	int keyidx;
-	struct crypto_ahash *tfm = tkey->tx_tfm_michael;
+	struct crypto_shash *tfm = tkey->tx_tfm_michael;
 	struct crypto_skcipher *tfm2 = tkey->tx_tfm_arc4;
-	struct crypto_ahash *tfm3 = tkey->rx_tfm_michael;
+	struct crypto_shash *tfm3 = tkey->rx_tfm_michael;
 	struct crypto_skcipher *tfm4 = tkey->rx_tfm_arc4;
 
 	keyidx = tkey->key_idx;
-- 
2.17.1